Booster vaccines protect hamsters with waning immunity from Delta VOC infection, disease, and transmission

Abstract

Waning immunity to COVID-19 vaccination is associated with increased risk of breakthrough infection, especially with highly transmissible variants of concern (VOC). Booster vaccination generates rapid immune recall in humans, which real-world observational studies suggest protects against VOC infection and associated disease, and modeling studies suggest could mitigate community spread. We directly tested the impact of booster vaccination on protection against Delta VOC infection, disease, and transmission to naive cohorts in golden Syrian hamsters. Animals with waning immunity to bnt162b2 generated rapid immune recall and strong protection against upper- and lower-respiratory tract infection when boosted with bnt126b2, mRNA-1273 or AZD1222. Boosting with either mRNA vaccine generated moderate protection against lung inflammation and virus transmission to unvaccinated animals. Our data support booster vaccination as a tool to address emerging VOC in the COVID-19 pandemic.

Syrian hamster convalescence from prototype SARS-CoV-2 confers measurable protection against the attenuated disease caused by the Omicron variant

“…Ultimately, this approach might identify an initial infectious dose and timepoint for rechallenge against waned immunity that could increase the discriminatory power of cross protection experiments using SARS-CoV-2 variants. Our results demonstrate that following infection, antibodies against the homologous virus remained high irrespective of the infectious dose administered, a finding consistent with other reports investigating waning immunity in the hamster [36][37][38][39]. As such, rechallenge of these hamsters at 50 days post-infection occurred against a high circulating antibody level (against ancestral virus) and, it might be assumed, a strong cellular immune component, the latter only being measured after rechallenge at termination.…”

Vaccination against SARS-CoV-2 Does Not Protect against the Development of Anosmia in a Hamster Model

“…These were selected as much of the American population received them during the early roll-out of vaccines. Additionally, the selected dosage schedule has been shown to induce significant seroconversion [27,28,32], confirmed in this study by protection against weight loss and viral clearance in the lung (Figure 2). However, this study was limited by inadequate sampling to determine neutralizing antibody concentrations.…”

“…Hamsters receiving vaccines were intramuscularly vaccinated on study days −35 and −14 with 5 µg of either Pfizer (BNT16b2) or Moderna (mRNA-1273) mRNA vaccines diluted in 100 µL of sterile phosphate-buffered saline (PBS) or 100 µL of sterile Dulbecco's Phosphate Buffered Saline (DPBS) (Sigma, St. Louis, MO) as an unvaccinated control. Vaccination doses were selected based on previous studies [27,28]. All hamsters were intranasally inoculated with 100 µL of either 10 4 PFU of SARS-CoV-2 diluted in sterile PBS or PBS as a mock control.…”

“…To determine whether prior vaccination would reduce the severity of anosmia, male hamsters were intramuscularly vaccinated in a prime/boost strategy with either 5 µg Pfizer (BNT16b2) or Moderna (mRNA-1273) mRNA vaccines or with PBS as an unvaccinated control (n = 8 per group). This dose and schedule was selected as it is within the accepted range for hamsters and has been shown to induce significant seroconversion [27,28]. Two weeks after the boosting vaccination, hamsters were intranasally inoculated with 10 4 PFU of either lineage A or BQ.1 SARS-CoV-2, or with PBS as a mock control.…”